General Engineering Principles I.

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General Engineering Principles ISealed Source & Device WorkshopGeneral Engineering Principles I: 1

General Engineering Principles IForces:Tensile and Compressive: Tensile (Tension) - pulling apart Compressive (Compression) - pushing together Forces may be direct, or may be caused by changes inpressure, temperature, or combined loads.Shear: Force perpendicular to the primary axis.Sealed Source & Device WorkshopGeneral Engineering Principles I: 2

General Engineering Principles IStrength: Stress Force/Area (psi or Pa) Strain Elongation under stress change inlength/original length (in(in./in.)/in ) Ultimate Strength: maximum stress sustained withoutbreaking - exceed this limit and the material will break. Yield Strength: maximum stress sustained withoutpermanent deformation - the material will stretch andcome back to its original length.Sealed Source & Device WorkshopGeneral Engineering Principles I: 3

General Engineering Principles IStress vs. Strain:Sealed Source & Device WorkshopGeneral Engineering Principles I: 4

General Engineering Principles IStrength (cont.):(Graphic – See Notebook)Sealed Source & Device WorkshopGeneral Engineering Principles I: 5

General Engineering Principles IStrength (cont.):Sealed Source & Device WorkshopGeneral Engineering Principles I: 6

General Engineering Principles IStrength (cont.):Sealed Source & Device WorkshopGeneral Engineering Principles I: 7

General Engineering Principles IDuctility: A metal is ductile when it can be drawn out intension without rupture (Opposite of Brittlemetals). A ductile metal must be strong and plastic. Ductile materials have large difference betweenyield and ultimate strengths. Lead wire is difficult to draw because thestrength of lead is low.Sealed Source & Device WorkshopGeneral Engineering Principles I: 8

General Engineering Principles IHardness: Resistance to local penetration, scratching,machining, wear or abrasion. Different measurement scales (Rockwell(Rockwell,Brinell, Vickers). Hard materials exhibit brittle, catastrophicfailure. Therefore, for very hard materials, thereis no indication of whether the component isclose to failure.Sealed Source & Device WorkshopGeneral Engineering Principles I: 9

General Engineering Principles IBrittleness: Is the property of breaking without muchpermanent distortion It may bbe ddue tto bbrittlenessittloff theth grainiboundaries or of the crystal themselves.Excessive presence of sulfur in steel makes itbrittle in elevated temperatures. When the phosphorus contents are too high insteels, they exhibit brittleness at coldtemperatures.Sealed Source & Device WorkshopGeneral Engineering Principles I: 10

General Engineering Principles IElasticity: The elasticity of a metal is its power of returningto its original shape after deformation by a force.Many materials behave to some extent likepowerful elastics, and, within limits, will recovertheir shape when load on them is removedremoved. For example, if the elastic limit of a materialwere 15 tons per square inch, then with bar ofmaterial 1 Sq. in. in area, the material wouldreturn to its original length from a load of 15tons. If this loading was exceeded, the materialwould permanently stretch.Sealed Source & Device WorkshopGeneral Engineering Principles I: 11

General Engineering Principles IElongation: When a material is pulled in a testing machinefor the purpose of finding its tensile strength,stretch takes place before the bar breaks. Theelongation is the amount of this stretch and isgenerally expressed as a percentage. If a metal length of 2 in. stretched to 2 3/4 in,before fracturing, the elongation would be,{(2 3/4 in. - 2 in.)/2} x 100 37 ½ per cent. A good elongation indicates a ductile material.Sealed Source & Device WorkshopGeneral Engineering Principles I: 12

General Engineering Principles IMalleability: This is a property of permanently extending inall directions without rupture by pressing,hammering rolling etc.hammering,etc It requires that the metal will be plastic but is notdependent on strength, e.g., lead is a verymalleable metal.Sealed Source & Device WorkshopGeneral Engineering Principles I: 13

General Engineering Principles IPlasticity: This is rather similar to malleability, and involvespermanent deformation without rupture. It is theextreme opposite of elasticityelasticity. Plasticity is necessary for forging, i.e., steel isplastic when at bright red heat.Sealed Source & Device WorkshopGeneral Engineering Principles I: 14

General Engineering Principles IToughness: Is the amount of energy a material can absorbbefore fracture A measure off theth toughnessthoff a metalt l may bebobtained by nicking it, placing it in a vise andstriking the end with a hammer. Certain woods are very tough. It is for thisreason that hickory is a good material forsledge-shafts.Sealed Source & Device WorkshopGeneral Engineering Principles I: 15

General Engineering Principles IMelting Points: Very important when discussing fires. Lead willusually melt in a fire. Important for seals and gaskets in hightemperatures. The seals and gaskets will berendered useless. Adhesives usually won’t survive well in hightemperatures.Sealed Source & Device WorkshopGeneral Engineering Principles I: 16

General Engineering Principles IThermal Expansion: Materials expand as temperature increases andcontract when temperature decreases. NNo voidid spaces, suchh as iin source capsules,lcould cause tension and possible rupture. Thermal cycling causes tension andcompression therefore the possibility of fatiguefailure. Could be caused by internal pressures(such as in sources) or in a member itself(concrete joints).Sealed Source & Device WorkshopGeneral Engineering Principles I: 17

General Engineering Principles IThermal Expansion: (Cont.)Sealed Source & Device WorkshopGeneral Engineering Principles I: 18

General Engineering Principles IMoments: Compressive forces at one edge and tensileforces at the other edge. Usually of concern when loads are appliedperpendicular to the primary axis of a rod orplate. Standard formulas for calculating moments. Example: Irradiator sources require a bendtests.Sealed Source & Device WorkshopGeneral Engineering Principles I: 19

General Engineering Principles ITorsion/Torque: Twisting of a component around it primary axis. Usually applies for turning a shaft, such as ashutter. The larger the lever arm, the greater the torque. A large weight that rotates at a large distancefrom the center of a shaft will create a largetorque.Sealed Source & Device WorkshopGeneral Engineering Principles I: 20

General Engineering Principles ISlenderness: The ability of the component to bend(sometimes referred to as buckling). Different than moments in that it is created by aload being applied along the primary axis. Length to Diameter ratio is usually veryimportant. The higher the ratio, the more likely itis to bend.Sealed Source & Device WorkshopGeneral Engineering Principles I: 21

General Engineering Principles IPoisson's Ratio: If a bar is subjected to a longitudinal stress therewill be a strain in this direction equal to E/Stress.There will also be a strain in all directions atright angles to the longitudinal stressstress. It is foundthat for elastic metals the lateral strain isproportional to the longitudinal strain, and is ofthe opposite type. The ratio Lateral strain / Longitudinal strain iscalled Poisson’s Ratio.Sealed Source & Device WorkshopGeneral Engineering Principles I: 22

General Engineering Principles INormalizing: The object of normalizing is to refine thestructure of steel and remove strains which mayhave been caused by cold working. Thisprocess isi necessary whenh steelt l iis kkeptt atthigher temperatures for prolonged periodsduring forging or cold working. If the steel is slowly heated to its annealingtemperature, the structure is in the most refinedstate, and normalizing consists of cooling in theair.Sealed Source & Device WorkshopGeneral Engineering Principles I: 23

General Engineering Principles IAnnealing: The purpose of the annealing is so that steelcan be more easily machined. To relieveinternal stresses which may have been causedb thbythe coldld workk or bby unequall contractionst tiiin acasting. The process involves heating slowly, andholding at a temperature long enough to enableinternal changes to take place and than coolingslowly. Annealing temperature is lower withincreasing carbon contents.Sealed Source & Device WorkshopGeneral Engineering Principles I: 24

General Engineering Principles IShape of Components: Beams - round, rectangular, solid or hollow Plate - is a rolled product more than 3.03 0 mmthick, supplied flat as in the case of a sheet. Itmay be hot rolled only, but in a thinner gauge itcan also be offered cold-rolled, when it will havebetter finish and closer tolerance than hot-rolledequivalent.Sealed Source & Device WorkshopGeneral Engineering Principles I: 25

General Engineering Principles IShapes of Components: (Cont.) Sheets and strips - are cold rolled products withgreater than 0.2 mm but notthickness gexceeding 3.0 mm. A sheet is supplied flat,where as strip is coil form. A sheet may,however, be manufactured as strip and cut tolength.Sealed Source & Device WorkshopGeneral Engineering Principles I: 26

General Engineering Principles IFatigue: May be caused by thermal cycling or vibration. Failure from repeated loading and unloading,where the loads are below the ultimate strengthof the material. Tensile stresses are more destructive thancompressive stresses.Sealed Source & Device WorkshopGeneral Engineering Principles I: 27

General Engineering Principles IFatigue (cont.):Sealed Source & Device WorkshopGeneral Engineering Principles I: 28

General Engineering Principles IEngineering Analysis: Used to evaluate design based on prototype testing of anearlier design and to verify adequacy of deviations intesting procedures or conditions. Used to extrapolate results to other products, for whichdesign and testing have been approved, such as a designseries or other conditions of use. Used to evaluate changes in the product design. Theseusually occur as part of an amendment request.Sealed Source & Device WorkshopGeneral Engineering Principles I: 29

General Engineering Principles ITypical Analysis: Finite Element Methods Cyclic Stress Analysis Heat Transfer Analysis Failure Analysis Safety AnalysisSealed Source & Device WorkshopGeneral Engineering Principles I: 30

General Engineering Principles IEnvironmental Effect on Metals:Atmosphere: most metals react with oxygen, particularly atelevated temperature chemical attack hydrogen & nitrogen embrittlementSealed Source & Device WorkshopGeneral Engineering Principles I: 31

General Engineering Principles IEnvironmental Effect on Metals:Radiation: Can affect internal structure of all materialscausing a breakdown in their properties (esp.lubricants, adhesives, gaskets, Teflon, etc.)Sealed Source & Device WorkshopGeneral Engineering Principles I: 32

General Engineering Principles IInteraction Of Neutron With Crystalline Structure:Sealed Source & Device WorkshopGeneral Engineering Principles I: 33

General Engineering Principles IEnvironmental Effect on Metals:Chemical: material dissolves or are attacked by corrosiveliquids, gasses, acids or alkalies leaching occurs when an element is removed asa result of corrosion (i.e., dezincification ofbrass)Sealed Source & Device WorkshopGeneral Engineering Principles I: 34

General Engineering Principles IEnvironmental Effect on Metals :Electrochemical: Formation of an electrochemical cell requires: an anode a cathode an electrolyteSealed Source & Device WorkshopGeneral Engineering Principles I: 35

General Engineering Principles IEnvironment Effect on Metals:Corrosion: Transfer of electrons form one species toanother metal ions characteristically lose or giveup electrons in an oxidation reactionM Mn neexample:Fe Fe 2eAl Al 3e Sites at which the oxidation reaction takes placeare the anodes.Sealed Source & Device WorkshopGeneral Engineering Principles I: 36

General Engineering Principles I Environmental Effect on Metals:Corrosion: The electrons generated from the oxidationprocess mustt bbe ttransferredfd becomebpartt offanother reaction known as the reductionreaction. (acid solution )2H 2e- H2 (gas) (aerated water)O2 2H2O 4e- 4(OH-)Sealed Source & Device WorkshopGeneral Engineering Principles I: 37

General Engineering Principles IEnvironmental Effect on Metals:Corrosion Cont. Example: Oxidation/rusting of iron in waterwhichhi h containst i didissolvedl d oxygen Fe ½ O2 H2O Fe2 2OH- Fe(OH)22Fe(OH)2 ½O2 H2O 2Fe(OH)3 Fe(OH)3 is an insoluble compound (rust) withnon-metallic elements.Sealed Source & Device WorkshopGeneral Engineering Principles I: 38

General Engineering Principles ISealed Source & Device WorkshopGeneral Engineering Principles I: 39

General Engineering Principles IEnvironmental Effect on Metals:Corrosion:Galvanic Corrosion Two metals or alloys having different compositions thatare electrically coupled while exposed to an electrolyte Examples: Steel/brass interface, copper/steel pipe fittingsPrevention If coupling of dissimilar metals is necessary, choosemetals that are close in the galvanic series Use an anode area as large as possible Electrically insulate the dissimilar metalsSealed Source & Device WorkshopGeneral Engineering Principles I: 40

General Engineering Principles IComparative Alloy Performance:Sealed Source & Device WorkshopGeneral Engineering Principles I: 41

General Engineering Principles IMetals and Effect of Alloying Elements:Carbon:hardenability, strength, hardness,and wear resistanceNickel:strength and toughness; minor effecton hardenabilityChromium:strength, toughness, hardness, andwear resistance, increases depth ofhardness penetration in heattreatmentSealed Source & Device WorkshopGeneral Engineering Principles I: 42

General Engineering Principles IMetals and Effect of Residuals:Residual elements during the processing of steelscan have various effects as outlined below:Nitrogen:strength, hardness, machinability(decreases ductility and toughness)Oxygen:slight increase in strength of rimmedsteels (gross reduction in toughness)Hydrogen:(severe embrittlement of steels)Sealed Source & Device WorkshopGeneral Engineering Principles I: 43

General Engineering Principles I(Graphic – See Notebook)Sealed Source & Device WorkshopGeneral Engineering Principles I: 44

General Engineering Principles ICarbon Steels - Properties:REF: Serope Kalpakjian, Manufacturing Processes for Engineering Materials, Addison Wessley, 1984, pp145.Sealed Source & Device WorkshopGeneral Engineering Principles I: 45

General Engineering Principles ICarbon Steels - Properties:REF: Serope Kalpakjian, Manufacturing Processes for Engineering Materials, Addison Wessley, 1984, pp147.Sealed Source & Device WorkshopGeneral Engineering Principles I: 46

General Engineering Principles IProperties of Selected Stainless Steels:R E F : D o n a ld R . A s k e la n d , T h e S c ien c e a n d E n g in e e r in g o f M a te r ia ls , P W S P u b lis h e rSealed Source & Device WorkshopGeneral Engineering Principles I: 47

General Engineering Principles IAluminum Alloys - Properties:REF: Serope Kalpakjian, Manufacturing Processes for Engineering Materials, Addison Wessley, 1984, pp154.Sealed Source & Device WorkshopGeneral Engineering Principles I: 48

General Engineering Principles IAluminum: lightweight good strength and thermal conductivity ggood corrosion resistance– resistant to concentrated nitric acid, organicacids, and sulfuric acid alloying, cold working and heat treatment canreduce corrosion resistance tensile strength 13,000 psi with 45% elongationSealed Source & Device WorkshopGeneral Engineering Principles I: 49

General Engineering Principles IAluminum: (cont’d) 1/3 the stiffness of steel poor wear resistance fatigueg strengthg low - 18,000,psip Two major groups: wrought and casting alloysSealed Source & Device WorkshopGeneral Engineering Principles I: 50

General Engineering Principles IBrass: alloy of copper and zinc known for its workability, resistance to variouscorrosive elements and their attractive finishes strength compares with that of mild steel much lower modules of elasticity than mild steel subject to cracking used as a shield in low energy gamma radiationand as source holdersSealed Source & Device WorkshopGeneral Engineering Principles I: 51

General Engineering Principles ICopper: good thermal conductor good corrosion resistance for normalatmosphere and calm, non-oxidizing water ease of fabrication copper does corrode rapidly and becomes brittledue to absorbed oxygen at elevatedtemperatures better strength and ductility than aluminum andmagnesium poor creep resistance and should only be usedat temperatures below 400 F (205 C)Sealed Source & Device WorkshopGeneral Engineering Principles I: 52

General Engineering Principles ILead: tensile strength of about 2500 psi corrosion resistance to sulfuric acid, watersewage and atmosphere highhi h ddensity,it specificifi gravityit off 1111.3333 low melting point subject to creep, creep starts to develop around500 psi used as a shield in medical and nuclearindustriesSealed Source & Device WorkshopGeneral Engineering Principles I: 53

General Engineering Principles ICarbon Steels: Generally grouped into three categories: Low-carbon ( 0.3% carbon) Medium-carbon (0.3 to 0.6% CARBON) High-carbonHigh carbon ( 00.6%6% carbon) AISI-SAE designation (4 digits): first two digits indicate the alloying element andtheir percentage, last two digits represent theamount of carbonSealed Source & Device WorkshopGeneral Engineering Principles I: 54

General Engineering Principles ICarbon Steels: (cont.) Ultimate tensile strength: range from 42,000 to282,000 psi. Elongation: approximations between 0-35% Brinell hardness: 80-490 Stress amplitude 30 to 112,000 psi Modulus of elasticity 20 - 30 million psi for allsteelsSealed Source & Device WorkshopGeneral Engineering Principles I: 55

General Engineering Principles IStainless Steels: Highly resistant to corrosion and oxidationMaintains considerable strength at elevated temperaturesCharacterized by their high chromium content ( 12% Cr)Wide range of propertiesFour main categories: Ferritic stainless steels (400 series)Martensitic stainless steels (400 and 500 series)Austenitic stainless steels (200 and 300 series)Precipitation-hardening stainless steels (P-H)Sealed Source & Device WorkshopGeneral Engineering Principles I: 56

General Engineering Principles IFerritic Stainless Steels (400 series): Good strengthExcellent corrosion resistanceModerate formability and ductilityRelatively inexpensivePoor weldabiltiySmall amounts of carbon and nitrogen aredetrimental to corrosion resistance(intergranular corrosion)Sealed Source & Device WorkshopGeneral Engineering Principles I: 57

General Engineering Principles ICommon stainless steels used in SSDs:18-8-This is a basic group of steels that areresistant to many types of corrosion. Thisgroup is so named for its composition of 18%chromium and 8% nickel.nickel304-This is a basic 18-8 steel with 0.08% carbon(maximum). It is less susceptible to carbideprecipitation when it is welded, therefore itmay be used over a wider range of corrosiveconditions without additional heat treatment.Sealed Source & Device WorkshopGeneral Engineering Principles I: 58

General Engineering Principles ICommon stainless steels used in SSD’s:304L-It was developed to minimize the amount ofcarbide pprecipitationpwith a carbon contentbelow 0.03%.

Sealed Source & Device Workshop General Engineering Principles I: 24. General Engineering Principles I Shape of Components: Beams - round, rectangular, solid or hollow Plate - is a rolled product more than 3 0 mmis a rolled product more than 3.0 mm thick, supplied flat as in the case of a sheet. It may be hot rolled only, but in a thinner gauge it can also be offered cold-rolled, when .

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